The State will lead evidence from a Perth lawyer about instructions he allegedly received from Lloyd Rayney in October 2007 to destroy a computer hard drive.
Defence lawyers yesterday lost their bid to set aside the witness summons for David Price, the lawyer who had been representing Mr Rayney over a telecommunications charge relating to the bugging of Corryn Rayney's home phone calls.
The Supreme Court was told prosecutors wanted to subpoena all documents regarding the instruction, which Mr Rayney gave on October 4, 2007.
Mr Rayney allegedly murdered his wife on August 7, 2007.
On September 20 that year, Mr Rayney was charged with bugging his wife's phone calls in the lead-up to her death.
Timothy Pearson has testified at the wilful murder trial that Mr Rayney paid him to bug the home phone and provide him with discs of his wife's taped calls that Mr Pearson showed him on a computer.
The State suggested yesterday the hard drive could have revealed the computer's history of activities and its destruction at Mr Rayney's request was a bid to destroy "legally admissible evidence of guilt".
Defence lawyer Anthony Elliott argued the hard drive had not contained such information.
He said it held extra copies of independent interviews with the Rayneys' two daughters, that were subject to "legal professional privilege" and aimed at preserving their evidence in case of litigation and a biased police investigation.